The present invention concerns a system of cooking and then cooling food products by a immersion in a heat transfer fluid, the said system being of the type consisting of a vessel and a system for homogenisation by blowing in gas bubbles.
In order to carry out the cooking of certain food products and in particular that of hams, one method consists of placing the hams in moulds which are deposited in a superimposed fashion in an enclosure which is closed by a cover. The enclosure is then filled with a heat transfer fluid previously heated and admitted so that it can suitably cook the hams. After cooking, the enclosure is drained of its fluid and is then filled with a previously refrigerated fluid in order then to cool the hams which have been cooked. At the end of cooling, the enclosure is drained once again, the cover is removed and the moulds are extracted from the enclosure and then discharged to an area for removing the hams from the moulds.
In order to homogenise the temperature of the heat transfer fluid in such an enclosure both in the cooking phase and in the cooling phase so as in particular better to control the said phases, it is known how to use means of homogenisation by blowing gas bubbles into the fluid contained in the said enclosure. More precisely, bubbles, generally air, are thus injected into the heat transfer fluid at the lower level of the enclosure, which creates a continual ascending stirring in it so that the measured temperature of the fluid, at various levels inside the enclosure, is homogeneous.
The problem nevertheless posed by this type of means of homogenisation by blowing in gas bubbles is the exchange of heat that may take place between the gas bubbles and the heat transfer fluid. This is because the gas used for blowing in the bubbles is at a temperature, for example ambient temperature, which is never that of the heat transfer fluid. Thus, generally in the case of a gas at ambient temperature, in the cooking phase, the heat transfer fluid is cooled by the gas blown in, and conversely, in the cooling phase, the heat transfer fluid is heated. The result is an extension of the phases mentioned above unless a compensation is made by a supplementary addition of heat or cold (according to circumstances) to the heat transfer fluid, which nevertheless gives rise to an excessive consumption of energy.